Heretofore, in the separation or concentration of an organic material-containing gas or liquid mixture, for example, a distillation method, an azeotropic distillation method, a solvent extraction/distillation method, and a separation method using an adsorbent are being performed. However, these conventional methods are disadvantageous in that a lot of energy is required or the target range to which separation or concentration can be applied is limited.
In recent years, a membrane separation or concentration method using a membrane such as polymer membrane has been proposed as a separation method replacing such a conventional separation method. The polymer membrane has excellent processability and includes, for example, a flat membrane and a hollow yarn membrane. However, the polymer membrane is disadvantageously low in the heat resistance. Also, many of polymer membranes exhibit poor resistance to chemicals and swell upon contact particularly with an organic material such as organic solvent and organic acid, and the target range to which separation or concentration can be applied is limited.
On the other hand, a membrane separation or concentration method using a membrane formed of an inorganic material such as zeolite membrane has been proposed. The zeolite membrane used for separation or concentration is generally a zeolite membrane composite obtained by membranously forming a zeolite on a support. For example, a mixture of an organic material and water is flowed to the zeolite membrane composite, and water is selectively allowed to permeate therethrough, whereby the organic material can be separated or concentrated. In the membrane separation or concentration using an inorganic material membrane, the amount of energy used can be reduced as compared with separation by distillation or an adsorbent and additionally, the separation or concentration can be performed in a wider temperature range than that with the polymer membrane and furthermore, can be applied also to the separation of an organic material-containing mixture.
As for the separation using a zeolite membrane, a method where a zeolite having hydrophilicity is utilized for selective permeation of water has been proposed. For example, there have been proposed a method of allowing selective permeation of water by using an A-type zeolite membrane composite to concentrate an alcohol (Patent Document 1), a method of allowing selective permeation of water from a mixed system of an alcohol and water by using a mordenite-type zeolite membrane composite to concentrate the alcohol (Patent Document 2), and a method of allowing selective permeation of water from a mixed system of acetic acid and water by using a ferrierite-type zeolite membrane composite to separate/concentrate the acetic acid (Patent Document 3).